Authentication apparatus and authentication method

1. An authentication apparatus comprising: a first determination section that determines whether a condition for determining that there is a possibility of an erroneous determination is satisfied based on information indicating the similarity between the shape of a biological part included in a biological image to be authenticated and the shape of a biological part included in a registration biological image; a change section that changes an aspect ratio of the biological image to be authenticated and registration biological image in the case where said condition is satisfied; and a second determination section that determines whether a person to be authenticated is a registrant based on the similarity between the shape of a biological part included in a biological image to be authenticated whose aspect ratio has been changed and the shape of a biological part included in a registration biological image whose aspect ratio has been changed.

2. The authentication apparatus according to claim 1 , wherein the biological part included in the biological image is the veins included in a vein image.

3. The authentication apparatus according to claim 1 , wherein the biological image is an image in which a biological part having a constant width and a background component are represented by binary values.

4. The authentication apparatus according to claim 1 , wherein the first determination section determines whether the similarity falls in a range defined with a threshold which is a limiting value for identifying a person to be authenticated as a registrant set as a criterion.

5. The authentication apparatus according to claim 1 , wherein the first determination section determines whether a condition for determining that there is a possibility of an erroneous determination is satisfied using first information indicating the similarity between a biological image to be authenticated and a registration biological image and second information indicating the similarity between images which are generated through conversion processing from the biological image to be authenticated and registration biological image and which each represent a state of a line component having a length not less than a predetermined length which is extracted from the biological part in the biological image.

6. The authentication apparatus according to claim 5 , wherein the first determination section determines whether the sum of the first information and second information satisfies the condition for determining that there is a possibility of an erroneous determination.

7. An authentication method comprising: a first step of determining whether a condition for determining that there is a possibility of an erroneous determination is satisfied based on information indicating the similarity between the shape of a biological part included in a biological image to be authenticated and the shape of a biological part included in a registration biological image; a second step of changing an aspect ratio of the biological image to be authenticated and registration biological image in the case where said condition is satisfied; and a third step of determining whether a person to be authenticated is a registrant based on the similarity between the shape of a biological part included in a biological image to be authenticated whose aspect ratio has been changed and the shape of a biological part included in a registration biological image whose aspect ratio has been changed.

8. An authentication apparatus comprising: an acquisition section that acquires a magnification ratio of a subject set in an image pickup section that has generated a biological image to be authenticated through image pickup operation and magnification ratio of a subject set in an image pickup section that has generated a registration biological image through image pickup operation; a change section that changes an aspect ratio of the biological image to be authenticated or registration biological image so as to make the magnification ratios acquired by the acquisition section equal to each other; a determination section that determines whether a person to be authenticated is a registrant based on the similarity between the shape of a biological part included in a biological image to be authenticated whose aspect ratio has been changed and the shape of a biological part included in a registration biological image whose aspect ratio has been changed.

9. An authentication method comprising: a first step of acquiring the magnification ratio of a subject set in an image pickup section that has generated a biological image to be authenticated through image pickup operation and magnification ratio of a subject set in an image pickup section that has generated a registration biological image through image pickup operation; a second step of changing the aspect ratio of the biological image to be authenticated or registration biological image so as to make the magnification ratios acquired by the acquisition section equal to each other; a third step of determining whether a person to be authenticated is a registrant based on the similarity between the shape of a biological part included in a biological image to be authenticated whose aspect ratio has been changed and the shape of a biological part included in a registration biological image whose aspect ratio has been changed.